1. Field of the Invention
The present invention relates to a drawing apparatus, and a method of manufacturing an article.
2. Description of the Related Art
A drawing apparatus using a charged particle beam such as an electron beam performs overlay drawing that draws a new pattern overlaid on a pattern (to be referred to as a “shot pattern” hereinafter) formed in each shot region of a substrate.
In the overlay drawing, first, a substrate is moved based on the designed array coordinate values of a plurality of shot patterns, and positions when some of the plurality of shot patterns are aligned to a reference position are actually measured. Next, assuming the designed array coordinate values of shot patterns and actual array coordinate values to align have a unique relation including a predetermined error, error parameters are decided such that the average deviation between the plurality of measured values and the actual array coordinate values to align is minimized. The actual array coordinate values of the shot patterns are obtained based on the error parameters and the designed array coordinate values of the shot patterns. The substrate is positioned in accordance with the actual array coordinate values, and a pattern is drawn.
In such overlay drawing, distortions (for example, expansion/contraction and rotation) of shot patterns are also measured as well as the actual array coordinate values of the shot patterns. The distortions of shot patterns occur due to factors of a lithography apparatus such as a drawing apparatus when forming a pattern or due to deformation of a substrate caused by a heat process when forming a pattern.
FIG. 5A is a view showing the array of 5 (rows)×5 (columns) shot patterns formed on a substrate SB. Actual shot patterns SP are indicated by solid lines, and designed shot patterns SP′ are indicated by broken lines. FIG. 5B shows a state in which overlay drawing is performed for the substrate SB (actual shot patterns SP) by a drawing apparatus including a plurality of charged particle optical systems CP1, CP2, and CP3. Referring to FIG. 5B, each of the charged particle optical systems CP1 to CP3 emits 5 (rows)×5 (columns) charged particle beams to the substrate SB. When a stage that holds the substrate SB is moved to the upper side with respect to the charged particle optical systems CP1, CP2, and CP3, the charged particle optical systems CP1, CP2, and CP3 draw stripe regions S1, S2, and S3, respectively (stripe drawing). In this stripe drawing, multiple irradiation is performed for the same positions of the substrate by the charged particle beams of the charged particle optical systems which are arrayed in the substrate moving direction. The irradiation is on/off-controlled, thereby controlling the irradiating doses of the charged particle beams on the substrate.
Each charged particle optical system includes a deflector configured to deflect charged particle beams. This deflector adjusts the positions of (drawing regions defined by) a plurality of charged particle beams on the substrate at once. In the stripe drawing, a new pattern is overlaid and drawn on the shot patterns while adjusting the positions of the drawing regions of the charged particle optical systems by the deflectors based on the actual positions of the shot patterns on the substrate.
However, depending on the size of the shot patterns, the drawing region of a charged particle optical system may extend over shot patterns adjacent in a direction perpendicular to the substrate moving direction (that is, located on both of two adjacent shot patterns), like the charged particle optical system CP3 shown in FIG. 5B. This poses the following problem. In fact, the shot patterns on the substrate are not always periodically arrayed along the designed array coordinates (that is, the positions of the shot patterns are shifted). It is therefore necessary to perform drawing while adjusting (correcting) the position of the drawing region with respect to the shot patterns. However, when the drawing region of a charged particle optical system extends over shot patterns adjacent in the direction perpendicular to the substrate moving direction, the position of the drawing region of the charged particle optical system can be corrected with respect to only one of the shot patterns.
To solve this problem, Japanese Patent Laid-Open No. 2004-172428 proposes a drawing apparatus capable of mechanically adjusting the distances between the optical axes of a plurality of charged particle optical systems.
In this conventional technique, however, the precision of mechanically adjusting the distances between the optical axes of the plurality of charged particle optical systems is not sufficient and cannot meet the overlay precision required in recent overlay drawing.